Those skilled in the art know that disc brake assemblies are commonly used for motor vehicles and comprise a rotor and an associated caliper assembly. One or more brake pads of the caliper assembly frictionally interface with the rotation of the rotor to slow its movement. Through the frictional interfacing of the brake pads with the rotor, the kinetic energy of the moving vehicle is converted to heat. The heat within the rotor leads to an unequal distribution of thermal stresses which distort the brake rotor. This process is known as coning. Coning can result in braking roughness and may be a factor that may lead to disc thickness variation.
Prior art rotor designs have attempted to reduce, or prevent, coning with limited success. For example, in U.S. Pat. No. 4,651,851 a brake rotor is provided with a flange attached to a hub assembly. A portion of the flange extends from the hub assembly to an inboard friction section. An outboard friction section is connected to the inboard friction section by a plurality of vanes. The portion of the flange extending from the hub to the inboard friction section is designed to act as a heat sink to offset the tilting of the inboard friction section toward the hub assembly. The described design, however, is problematic since heat induced during braking will increase the outer diameter of the outboard friction section at a greater rate than that of the inboard friction section connected to the heat sink. The result will be that the rotor will cone toward the inboard direction.
In U.S. Pat. No. 6,354,409 a brake rotor is provided having a central portion and an extending portion located at the periphery of the central portion. A friction portion having a first friction plate is attached to the extending portion and a second friction plate is attached to the first friction plate. This design is also problematic since heat induced during braking will increase the temperature of the inboard friction section at a greater rate than that of the outboard friction section connected the heat sink. The result will be that the rotor will cone toward the outboard direction.
In U.S. Pat. No. 5,544,726 a brake rotor is provided comprising a hub portion connected to the inboard and outboard friction surfaces. The inboard and outboard friction surfaces are both connected to the hub with individual solid portions. An air inlet port for the outboard friction surface is axially aligned with an air inlet port for the inboard friction surface to allow air to enter into the rotor. The air inlet ports for both friction surfaces alternate with the solid portions. The disadvantage of this design is that the portions connecting the inboard and outboard friction sections to the hub may be too weak to adequately support the rotor.